Automatic Transmission Ratio Shift Control for Torque Hole Elimination
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Solution Overview
Problem
Conventional automatic transmissions experience a 'torque hole' during upshifting, causing unpleasant shift shocks due to momentary activation of two torque flow paths and subsequent decrease in output shaft torque.
Innovation Solution
A transmission ratio control system that uses software-based algorithms to self-calibrate oncoming clutch torque capacity and decouple engine torque control from clutch torque control, allowing the off-going clutch to slip during the torque phase and seamlessly transition to the inertia phase, thereby eliminating or reducing the torque hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If simultaneous engagement of oncoming clutch and disengagement of off-going clutch is used during upshift, then ratio change is achieved, but torque hole occurs causing shift shock
Solution Approach 1:
The controller pre-conditions the oncoming clutch by gradually increasing its torque capacity before full engagement, and pre-reduces the off-going clutch torque capacity before disengagement. This preliminary preparation ensures that when the clutch swap occurs, the torque transition is smooth and prevents the sudden torque drop that causes shift shock.
Solution Approach 2:
The controller dynamically adjusts the torque capacity parameters of both clutches during the upshift event. By continuously modifying the torque capacity of the oncoming clutch from low to high and the off-going clutch from high to low, the system maintains optimal torque distribution throughout the transition, eliminating the torque hole phenomenon.
2Reliability
If oncoming clutch torque capacity is increased during torque phase, then engagement is prepared, but output shaft torque drops causing torque hole
Solution Approach 1:
The controller continuously monitors the torque capacity of both clutches and adjusts the oncoming clutch engagement rate based on feedback from the off-going clutch disengagement status. This closed-loop control ensures that the increase in oncoming clutch torque capacity does not cause an excessive drop in output shaft torque, maintaining power delivery smoothness while ensuring reliable engagement.
3Productivity
If conventional clutch control is used, then upshift is achieved, but unpleasant shift shock is perceived by vehicle occupant
Solution Approach 1:
The controller implements dynamic control of clutch torque capacity throughout the upshift event, transitioning from static conventional control. The torque capacity of each clutch is continuously adjusted based on the phase of the shift event (preparation, execution, completion), creating a smooth dynamic transition that eliminates shift shock while maintaining efficient upshift execution.
Data Source
AI summary
A control system and method for controlling a multiple gear ratio automatic transmission in a powertrain for an automatic transmission having pressure activated friction torque elements to effect gear ratio upshifts. The friction torque elements are synchronously engaged and released during a torque phase of an upshift event as torque from a powertrain source is increased while allowing the off-going friction elements to slip, followed by an inertia phase during which torque from a powertrain source is modulated. A perceptible transmission output torque reduction during an upshift is avoided.